Positive active material and method of preparing same and rechargeable lithium battery including same

Abstract

Disclosed are a positive active material that includes a core particle including a lithium-containing compound configured to reversibly intercalate and deintercalate lithium, and a coating layer on a surface of the core particle, the coating layer including a material including a carbon-fluorine (C—F) bond, a method of manufacturing the same, and a rechargeable lithium battery including the positive active material.

What is claimed is: 
     
       1. A positive active material, comprising:
 a core particle comprising a lithium-containing compound configured to reversibly intercalate and deintercalate lithium; and 
 a coating material comprising a fluorine-bonded carbon nanostructure comprising a fluorine-bonded carbon nanotube comprising a carbon-fluorine (C—F) bond, wherein the coating material is directly on a surface of the lithium-containing compound of the core particle. 
 
     
     
       2. The positive active material of  claim 1 , wherein the coating material further comprises a fluorine-bonded graphene, a fluorine-bonded carbon black, a fluorine-bonded graphite, a fluorine-bonded acetylene black, a fluorine-bonded carbon fine powder, a fluorinated organic material, or a combination thereof. 
     
     
       3. The positive active material of  claim 1 , wherein the fluorine-bonded carbon nanostructure comprises the C—F bond, and the C—F bond of the fluorine-bonded carbon nanostructure exhibits a peak in a range of about 950 cm −1  to about 1350 cm −1  as measured by FT-IR spectroscopy. 
     
     
       4. The positive active material of  claim 1 , wherein:
 the core particle further comprises carbon; and 
 the C—F bond of the coating material is formed from at least a portion of the carbon of the core particle, and exhibits a peak in a range of about 1150 cm −1  to about 1160 cm −1  as measured by FT-IR spectroscopy. 
 
     
     
       5. The positive active material of  claim 1 , wherein the core particle further comprises carbon, and the coating material further comprises LiF. 
     
     
       6. The positive active material of  claim 5 , wherein the LiF exhibits a (111) peak at a 2θ value of about 39°, a (200) peak at a 2θ value of about 45°, and a (220) peak at a 2θ value of about 63° as measured by X-ray diffraction (XRD) analysis. 
     
     
       7. A method of manufacturing a positive active material, the method comprising:
 preparing a lithium-containing compound configured to reversibly intercalate and deintercalate lithium; and 
 forming a coating layer directly on a surface of the lithium-containing compound, the coating layer comprising a coating material comprising a fluorine-bonded carbon nanostructure comprising a fluorine-bonded carbon nanotube comprising a carbon-fluorine (C—F) bond. 
 
     
     
       8. The method of  claim 7 , wherein the forming the coating layer comprises:
 fluorinating the surface of a carbon particle to form a fluorinated carbon particle; and 
 coating the surface of the lithium-containing compound with the fluorinated carbon particle. 
 
     
     
       9. The method of  claim 8 , wherein the carbon particle comprises a carbon nanostructure comprising a carbon nanotube. 
     
     
       10. The method of  claim 8 , wherein the fluorinating the surface of the carbon particle comprises:
 supplying a fluorine-containing gas and an inert gas at a ratio in a range of about 5:95 to about 95:5 (v/v) at a temperature in a range of about 25° C. to about 500° C. to the carbon particle. 
 
     
     
       11. The method of  claim 7 , wherein the forming the coating layer comprises:
 forming a carbon thin layer on the lithium-containing compound; and 
 fluorinating the carbon thin layer. 
 
     
     
       12. The method of  claim 11 , wherein the forming the carbon thin layer on the lithium-containing compound comprises:
 preparing a mixture of the lithium-containing compound and a carbon precursor to form a mixture; and 
 heat-treating the mixture. 
 
     
     
       13. The method of  claim 12 , wherein the carbon precursor is included in the mixture in an amount in a range of about 0.1 wt % to about 30 wt % based on the total amount of the mixture. 
     
     
       14. The method of  claim 11 , wherein the fluorinating the carbon thin layer comprises:
 supplying a fluorine-containing gas and an inert gas at a ratio in a range of about 5:95 to about 95:5 (v/v) to the carbon thin layer at a temperature in a range of about 25° C. to about 500° C. 
 
     
     
       15. The method of  claim 7 , wherein the forming the coating layer comprises directly fluorinating the surface of the lithium-containing compound. 
     
     
       16. A rechargeable lithium battery, comprising:
 a positive electrode comprising the positive active material according to  claim 1 ; 
 a negative electrode; and 
 an electrolyte. 
 
     
     
       17. The rechargeable lithium battery of  claim 16 , further comprising:
 a LiF film formed on the surface of the positive electrode. 
 
     
     
       18. The rechargeable lithium battery of  claim 17 , wherein the LiF film exhibits a binding energy peak in a range of about 685 eV to about 690 eV in an X-ray diffraction (XRD) analysis. 
     
     
       19. The positive active material of  claim 1 , wherein the coating material further comprises a fluorine-bonded carbon nano fiber, a fluorine-bonded carbon nano ribbon, a fluorine-bonded carbon nano bead, or a combination thereof. 
     
     
       20. The method of  claim 9 , wherein the carbon particle further comprises graphene, carbon black, graphite, acetylene black, a carbon fine powder, an organic material, or a combination thereof.